1. Field of the Invention
This invention relates to the field of compositions that are intended to change state from a flowable to a less flowable substance after application to an intended use and more particularly to compositions wherein it is desirable for this change of state to take place as rapidly as possible.
2. Background Information
The invention disclosed herein is a continuation in part of work previously accomplished and for which copending patent applications were filed on Jul. 15, 1988 as Ser. Nos. 07/219,522 pending and 07/219,523, now abandoned the disclosures of which are hereby incorporated by reference. The present invention is related to electroviscous fluids in a way that will be discussed below. My copending application Ser. No. 07/219,522 pending disclosed an induced dipole electroviscous fluid, comprising a dielectric fluid and a multiplicity of electrically polarizable aggregate particles dispersed in the dielectric fluid. Within the fluid, a substantial portion of the aggregate particles each further comprise a core and an electrically nonconductive shield, the core being at least partially electrically conductive and the shield partially encompassing the core and adapted to prevent particle to particle transmission of electric current. Alternately, the shield further comprises a shell for completely encapsulating the core. When an encapsulating shell is used, the core of the aggregate particle may be an electrolyte, the purpose of the shell in this instance being to prevent the electrolyte from migrating into and degrading the dielectric fluid. The performance of the electroviscous fluid is enhanced by incorporating in each aggregate particle at least one buoyant body, the purpose of the buoyant body being to equalize the effective density of the aggregate with the density of the dielectric fluid, thus enhancing the ability of the aggregate to stay in suspension for long periods of time. Buoyant bodies may be created as gas pockets in the shield or adhesively attached to the core using such as for example, glass microspheres or hollow plastic bodies. Glass microspheres having a density of 0.2 g/cc are especially useful as buoyant bodies. The core is made of any convenient conductive or semiconductive material and when a shell is used, the core can be a liquid or composite electrolyte.
Electroviscous fluids refer to fluids which exhibit the property of increased viscosity when the fluid is subjected to an electric field. One phenomenon for electrically controlling the viscosity of a fluid is commonly known as the Winslow effect. The term Winslow effect refers to the phenomenon of electrically controlling the viscosity of a fluid comprising a suspension of finely divided electrically polarizable matter in a dielectric fluid by subjecting the fluid to an electric field. Within this disclosure and the appended claims, the finely divided electrically polarizable matter is referred to as aggregate.
Numerous types of electroviscous fluids and aggregates are disclosed in my copending applications referenced above as well as in the prior art. Electroviscous fluids and aggregates for electroviscous fluids are disclosed in the prior art in U.S. Pat. Nos.: 4,687,589; 3,427,247; 3,970,573; 3,984,339; 4,502,973; 4,737,886, the disclosures of which are hereby incorporated by reference.
It is known that molded articles can be made by pouring a phase changing vehicle into a form, allowing the vehicle to set or cure and then removing the molded article from the mold. As used herein the term phase changing vehicle applies to any composition which changes state from a flowable to a less flowable or solid state when such compositions cure or set in the normal course of their use. Numerous commercially available compositions are available which exhibit such phase changing characteristics, examples of which are hereinafter disclosed. These include vehicles made from mixing multipart constituents which chemically react and vehicles having a contituent or a composition of constituents which reacts with its surroundings such as for example air.